Proposed caudal appendage classification system; spinal cord tethering associated with sacrococcygeal eversion

Area of Science:

• Pediatric Neurosurgery
• Developmental Biology
• Medical Imaging

Background:

• The existing classification of caudal appendages (human tails) from the 1980s is outdated due to advances in neuroimaging and increased case reports.
• Sacrococcygeal eversion, a retroverted curvature of sacral and coccygeal vertebrae, can present as a caudal appendage and has not been previously linked to spinal cord tethering.

Purpose of the Study:

• To re-evaluate the classification of caudal appendages in light of modern understanding and neuroimaging capabilities.
• To investigate the association between sacrococcygeal eversion and spinal cord tethering.
• To propose an updated classification system for caudal appendages.

Main Methods:

• Review of pediatric neurosurgery cases with "true" caudal appendages since 2000.
• Review of sacrococcygeal eversion cases since 2000.
• Electronic medical record search using terms "caudal appendage" and "persistent human tail."

Main Results:

• Nine "true" tails were identified, all associated with spinal cord tethering or possible tethering; six had a low-lying conus medullaris.
• Eight cases of sacrococcygeal eversion were found, with some linked to specific syndromes (Apert, Pfeiffer, Goldenhar, Turner) and potentially tethering lesions.
• Four cases of sacrococcygeal eversion without known syndromes were identified, two with associated tethering or potentially tethering lesions.

Conclusions:

• "True" caudal appendages are often cutaneous markers of spinal dysraphism and spinal cord tethering, rather than true embryonic tail remnants.
• Sacrococcygeal eversion can be associated with spinal cord tethering.
• A new five-category classification system for caudal appendages was developed: soft-tissue, bony, bony prominences, true tails, and other.